A breast pump is a device used by mothers for expressing their breast milk into a baby feeding bottle. Such devices can be either manually operated or automated by incorporation of, for example, an electric motor to drive the device. Such devices often include a flexible membrane which is moved up and down to create a negative pressure in a vacuum chamber of the breast pump, and include a rack and pinion mechanism in which the pinion rotates back and forth to move the rack, which is connected to the membrane, linearly back and forth to generate the negative pressure. Alternatively, a crank shaft or cam/eccentric element may be employed to move the membrane back and forth to generate the negative pressure.
It is known that the hormone ‘prolactin’ which promotes the milk ejection reflex is only effectively produced when the mother is in a relaxed condition. However, it can be unpleasant and/or uncomfortable for a mother to use a breast pump as it can feel unnatural since the device may feel and sound overly ‘mechanical’. Therefore, the discomfort and/or unnatural feel of using the breast pump may not put the mother at ease and may make her feel anxious, thereby affecting her capability to express milk for her baby.
Furthermore, the above-mentioned known mechanisms for negative pressure creation in known breast pumps include sliding surfaces and/or frictional contact which produce wear and/or may require lubrication to minimize wear. These mechanisms may create mechanical noise themselves and can also effectively transmit vibrations of the motor and gearbox to the outside structure of the breast pump such as the housing and/or milk collection bottle.
Reference WO 2005/016409 discloses a breast pump utilizing a rack and pinion type mechanism to generate linear movement for operation of the breast pump piston and cylinder. US2001/0038799 discloses a breast pump that has a durable drive chain comprising a drive shaft fit with an eccentric cam, to which is attached a follower. The follower being pivotably connected to a puller that is attached to a flexible diaphragm for creating a negative pressure in the breast pump.